It is known to provide a failure diagnosis system in a vehicle with advanced electronic control. The failure diagnosis system monitors whether or not a device of the vehicle is operating normally (i.e., whether a malfunction occurs). When the vehicle detects malfunction of the monitored device, the failure diagnosis system stores the malfunction data in memory such that control of the device reflects the malfunction content and/or such that the malfunction can be analyzed at a later time. For instance, U.S. Pat. No. 5,357,790 (Japanese Patent No. 2595819) discloses an internal combustion engine vehicle that has a system for diagnosing misfire (i.e., combustion failure) of the internal combustion engine.
Many vehicle failure diagnosis systems include a diagnosis processing section for executing failure diagnosis processes and an independent data managing section for managing the diagnosis result. When execution conditions are met for failure diagnosis, the diagnosis processing section outputs an execution demand for failure diagnosis to the data managing section, which in turn provides execution permission for the failure diagnosis, and then failure diagnosis commences. As such, early diagnosis of the failure may not occur.
For example, with the misfire detection system of U.S. Pat. No. 5,357,790, it can be difficult to detect misfiring at the time of engine starting. Misfiring detection is, however, permitted after fully starting the engine. In other words, misfiring detection is not performed at the time of engine starting, and a misfire may go undetected.
Furthermore, in a system where it is possible to execute the failure diagnosis process at cranking time of the internal combustion engine, failure diagnosis of a starter relay (i.e., power supply control system of a starter)), etc., the failure diagnosis processing is started after transmission of the execution permission. Therefore, failure diagnosis processing can be delayed undesirably, and the failure may not be detected.
Moreover, the diagnosis processing section and the data managing section are typically incorporated in a microcomputer of the engine control unit (ECU). Typically, the calculation cycle of the data managing section is a relatively slow cycle (e.g., 256 ms cycle) to avoid an excessively large calculation load of the ECU. As a result, output of the execution permission from the data managing section can be additionally delayed due to this relatively slow calculation cycle. Therefore, there may be significant delay between the time at which the execution condition is met and the start of failure diagnosis, and failure may go undetected.